It is known that a soldering tip can be heated by means of a current-carrying resistor, e.g., a wound coil or an arbitrarily shaped resistance wire. Heat transfer between the current-carrying resistor and the soldering tip can advantageously be accomplished, especially when the resistor is in direct contact with the soldering tip. However, the resistor provided for heating the soldering tip is subject to increased wear, especially when high currents are temporarily conducted therethrough. Another negative aspect is that the production of current-carrying wound resistors is expensive and that wound resistors are difficult to install in the soldering iron. In addition, current-carrying resistors require a certain warm-up time for heating the corresponding soldering tip to its operating temperature. Also, the material properties of the current-carrying resistor may change over time due to the repeated application of current, which may lead to non-uniform heating of the soldering tip, whereby the work result may deteriorate. This may, for example, have a negative influence on the quality of the soldering seam.
For accomplishing a focused, high, as well as fast, heat input in the workpieces to be processed, laser soldering processes are used in practice. Laser soldering is preferably used in automated processes by means of robots. This is due to the fact that a laser beam must be guided by the robot precisely along the workpieces to be processed so as to keep the heat input through the laser beam constant. Note that it is essential that the laser beam is guided at a constant distance from the soldering joint so as to prevent damage to the workpieces.
In the case of hand-held laser soldering irons, the laser beam exits the soldering iron and impinges directly on the workpieces to be processed. The exiting laser beam may, if used improperly, cause serious injuries to the user and damage to the workpieces to be processed.
In view of an increased risk of injuries and inadequate results in the processing of workpieces, hand-held laser soldering irons have been used very rarely up to now. This is especially also due to the fact that the precision with which the user can guide the hand-held soldering iron across the workpieces to be processed is much lower than that which can be achieved by means of a robot.
DE 40 17 286 A1 discloses a laser device with a soldering tip including a blind hole having a light conductor inserted in the open end thereof. At an end located adjacent the working end, the blind hole can be tapered, and the laser energy exiting the light conductor enters the hole adjacent the working end of the soldering tip and is there converted into thermal energy used for heating the working end of the soldering tip.
DE 196 01 181 A1 discloses a soldering device with a soldering tip configured as a hollow body and having a light-absorbing internal surface onto which a laser beam is directed via a light conductor. The temperature of the soldering tip is measured by means of a temperature sensor fixed to the outer wall of soldering tip, the measuring signal being adapted to be supplied to a laser control unit via a connection line.
U.S. Pat. No. 5,948,286 discloses a soldering device comprising a laser unit, an ultrasonic unit, and a soldering tip in the interior of which a light conductor is guided. The light conductor ends a short distance before the closed end of the soldering tip, whereby a gap having a size of approximately two to ten millimeters is formed.
U.S. Pat. No. 5,904,868 discloses a laser tool with a soldering tip heated by means of laser beams. The soldering tip has provided therein a blind hole for accommodating an electrical component. By means of the soldering tip heated by laser beams, the electrical component can be secured to and released from a substrate. At one end of the soldering tip, a laser energy absorbing material is provided, which establishes a thermal bridge to the component.
U.S. Pat. No. 5,565,119 discloses an apparatus including a plurality of laser soldering tips, each of these soldering tips being configured as a hollow element and heated by laser beams. In this apparatus soldering work can be done simultaneously at several points.
EP 0 150 305 B1 discloses an apparatus for bonding circuit elements, comprising a soldering tip which receives a laser beam, the energy of the laser beam being absorbed for heating the soldering tip. For an improved absorption degree of the laser energy, the internal surface of the soldering tip includes a black body surface.
EP 0 367 705 A2 discloses an ultrasound-assisted laser soldering apparatus. The laser soldering apparatus includes a soldering tip configured as a hollow element and providing an open end as well as a closed end. A ceramic sleeve is arranged in the interior of the soldering tip for holding a light conductor. Optionally, the soldering tip provides an absorbent coating applied to the closed end of the soldering tip. The optical coating allows particularly fast heating of the conical end of the soldering tip, an effect which, optionally, may additionally be enhanced by a roughened surface.
WO 2009/156505 A1 discloses a device for soldering metallic components, including a nozzle body having a transfer element at one end thereof, the transfer element being configured as a contact pressure device. The transfer element transfers thermal energy to the components to be joined.
Heating the soldering tip quickly and uniformly and keeping it on a constant temperature level is difficult in the case of known laser devices. Also, in known soldering devices, the material properties of the soldering tip may change in the course of time due to direct irradiation of the soldering tip with a laser beam, and this change of material properties may lead to irregular operating results.
In the light of the problems described with reference to the known prior art, three remains a need for a soldering iron which, by means of simple structural features, is ready to operate within a short period of time and offers a high soldering capacity without becoming dangerous for the user. Advantageously, the device would provide an efficient and low-priced method of heating a soldering iron quickly to its operating temperature.